Mycoplasma gallisepticum; PLEASE help

So, we have 2 hens that we bought a year ago from a local gal. Both have been healthy birds with no problems. Then this past April, we got 2 chicks from Wilco and one 3 week old chick from the same gal we bought our original 2 hens from a year ago.

When I picked up the 3 week old, it was in a parking lot and I was afraid the bird might jump out so I barely peeked in at her before taking her home. Upon getting back to the house, I took her out and she was gasping for air and sneezing repeatedly. I started making calls and could find no one who sees chickens, so after several discussions on the chicken groups I belong to, I decided to put her on amoxicillin and VetRx. For a few days she barely ate and continued with the symptoms of illness, but then slowly she started turning around and getting better. We have had her for a month now and have kept her in our office the entire time, away from the other birds.

A couple weeks ago the WSU Avian Lab suggested we test her for Mycoplasma gallisepticum ......the results were positive. At this point, we had resigned ourselves to keep her as a house chicken, but just for the heck of it we tested 3 out of the other 4 birds we have here.....one of the hens that we got a year ago and both of the chicks we bought at Wilco. The older hen and the little female both tested positive, while the rooster tested negative. None of those birds however, have ever shown any signs of illness so I guess they would be considered "carriers". None have been vaccinated against this disease.

My dilemma is this; Emma, the chick that was so ill, is almost symptom free now...she occasionally sneezes, but other then that, she is ok. Is it safe to introduce her to the other birds? Is a "carrier" the same thing as a bird who has actually become symptomatic? I don't want to make the others ill......but if they are carriers, perhaps I am worrying needlessly?

I know stress can cause this virus to flare up.....and I know that tetracycline is used to treat the symptoms, though it doesn't kill the actual virus. Do birds with this have a history of shorter lifespans?These birds are beloved pets, so please don't suggest we cull them.

Since several have tested positive, then your whole flock has been exposed. It won't matter if you go ahead and introduce the newest chicken. You should close your flock to new birds and birds going out. Many people have flocks that are MG positive--some know it and some don't. Most hatcheries are not totally MG free. That said, many will cull sick birds rather than treat them. But in small backyard flocks, some manage to avoid the disease by keeping the chickens healthy with good food, probiotics, keeping water clean and conditions in the coop good. Good air circulation, dry bedding, fans during hot weather, and plenty of room can do a lot in preventing diseases.